Conventionally, rosins and their derivatives, i.e., rosin esters are used as tackifiers for adhesives or pressure sensitive adhesives, modifiers for rubbers or plastics, resins for traffic paints, sizes for paper making, emulsifiers for synthetic rubbers, resin materials for inks and resins for paints, and the like. The above-mentioned rosin compounds are insufficient in views of their yellow or yellowish brown color, odor, and heat stability and weatherability (hereinafter both properties may be sometimes referred to as "stabilities").
In order to solve the defects of the rosin compounds, there have been commercially available, for example, disproportionated rosins which are improved in heat stability by disproportionation of raw rosins, hydrogenated rosins which are improved in the stabilities to a certain extent by hydrogenating raw rosins, or esterified rosins prepared by using the disproportionated rosins or the hydrogenated rosins. Those are, however, insufficient in views of color and stabilities.
There is described in JP-B-33771/1970 and JP-B-20599/1974 a process for disproportionation of rosins or rosin compounds with the particular organic sulfur compounds. The disproportionated rosins obtained according to that process are, however, insufficient in views of color, odor and stabilities.
As mentioned above, every conventional rosin, disproportionated rosin and hydrogenated rosin cannot simultaneously satisfy all the properties, i.e., color, odor and stabilities. Accordingly, it has been desired to produce colorless and odorless rosins having good stabilities.
An object of the present invention is, considering the above circumstances, to provide a novel process for producing colorless rosins which are improved in the properties of color, odor and stabilities of the conventional rosins.